The invention relates to wrenches for breaking drill pipe joints and more specifically to a pair of wrenches rotatably mounted on the drilling frame, one being hydraulically actuated for making and breaking the threaded joints when adding to or removing drill pipe sections which make up a string of drill pipe in a lightweight horizontal boring rig.
Conventional drill pipe sections utilized on all types and size of drilling rigs consists of an externally tapered threaded pin on one end of the section with a mating internally threaded box on the opposite end for receipt of the pin of the next section. These tapered threaded couplings, generally called tool joints, require some form of wrench means to tighten up the joints as well as break them loose. In rotary table conventional oil field drilling rigs, tapered slips are utilized to grip and hold the drill pipe with the weight of the drill pipe holding the slips engaged. In a George E. Failing Company catalog, section 4, page 9, a non tapered roller slip assembly is shown, which is utilized in a breakout table. These roller slips are actuated into engagement by rotating the breakout table with its square shaped camming surface.
Another commonly used locking device are oil field tongs which grab in only one direction and must be flipped over to work in the opposite direction.
Another wrench means is the fixed jaw wrench as illustrated in Alexander U.S. Pat. No. 3,239,016. While fixed jaw wrenches do work in both directions, their primary disadvantage is that they require that a pair of flats must be machined into the outer surface of both ends of all sections of the drill pipe which substantially increases the drill pipe cost.
Another method of breaking joints is the utilization of conventional pipe wrenches which are limited in the torque they can apply with also the danger of slipping under torque.